Larcan DTR10SC Installation and operating manual

GENERAL INFORMATION AND INSTALLATION
CONTENTS
GENERAL INFORMATION........................................................................................................................................... 1
1
2 GROUNDING/EARTHING ............................................................................................................................................. 2
3 LIGHTNING AND OTHER TRANSIENT PROTECTION .........................................................................................4
4 ABOUT POWER WIRING ..............................................................................................................................................5
5 VENTILATION/AIR CONDITIONING INFORMATION ..........................................................................................6
6 FIRE PROTECTION........................................................................................................................................................7
7 UNPACKING.....................................................................................................................................................................8
8 TRANSMITTER EXTERNAL INTERLOCK CONNECTIONS................ERROR! BOOKMARK NOT DEFINED.
9 FIRST-TIME, ON-SITE TRANSMITTER START-UP PROCEDURE......................................................................9
PUB14-01Rev 0 April 10, 2014 i DTR10SC General Information & Installation
GENERAL INFORMATION AND INSTALLATION
1 GENERAL INFORMATION
Applications Engineering support offered by LARCAN includes technical information, recommendations on vendor products when requested, and advice on project task considerations and time span estimation. This assistance is available upon request.
Although general application information is included in this manual, it is important that specific system layouts be prepared and that locations of cabinets and RF equipment, such as RF patching or switching equipment, are determined together with the routing of the transmission line, AC power (Mains) feeds and other wiring, grounding (earthing), and ventilation air ducting. Lightning protection should be considered early in the planning process, becau se a good building layout can offer significant benefit.
The DTR10SC series transmitter is a single chassis transmitter intended for rack mounting in a standard 19" cabinet. Since this type of product is often supplied for standby use or in unattended isolated site locations and therefore it is anticipated that any rack mounting arrangement pre-exists and is supplied by the customer. The installation of the DTR10SC must take into account ventilation considerations as outlined further in this document. That said, please not e the ventilation openings of the cabinet should be fitted with air filters, to help the transmitter components remain clean. Also because of the small size of this product a tabletop style of cabinet can be used and may be preferred.
Due consideration must be given to ventilation, as proper cooling ensures the longest equipment lifetime. Basic cooling information is provided, but if a higher powered transmitter is also on site, an experienced air conditioning contractor should be consulted.
Ensure that sufficient space is available both in front and rear of all cabinets and other equipment to permit easy access while equipment is being moved around, and to enhance accessibility for future maintenance. A minimum 90 to 100cm (about 3 to 3½ feet) of clearance is recommended to allow access for a technician and test equipment, but you may need more clearance for other reasons or for the lifting devices sometimes used during installations. You may wish to consult local equipment rental agencies for dimensions of their available lifting apparatus; the required clearance is one of the "planning" items to be considered.
All cabinets should be level. An uneven floor surface can distort the sheet metal frames of many cabinets so that door latches will not operate properly.
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GENERAL INFORMATION AND INSTALLATION
2 GROUNDING/EARTHING
For safety, it is important that grounding conductors of adequate size be used to connect the transmitter (and other) cabinet(s) to the station "technical ground" point. The following notes are supplied as a guide to grounding at full­service transmitter installations but are useful for all cases.
The metal bulkhead plate through which all circuits and coax lines to and from the tower will pass, makes an excellent technical ground because it will be connected with one or two, 150mm wide x 1.5mm thick copper straps to the tower ground system.
One method is that in which copper bar 75 or 100mm wide and the same thickness as the floor tile is laid under transmitter and other cabinets for grounding. Each cabinet rack or tabletop cabinet is then connected with 1.5mm copper strap or automotive starter cable to the copper ground bar. The copper bar in turn connects to the metal bulkhead plate. Alternatively, copper strap can be laid in a grounded overhead cable tray. Indoor grounding conductors must ultimately connect to the bulkhead plate.
Consult your electrical code book, or ask your electrical contractor about the minimum permissible ground conductor size, but for broadcast installations a low ground impedance is desirable, so generally the cross section of each cabinet ground should be the same or larger than the total of its AC wiring cross section.
All outdoor ground connections should be well bonded using an exothermic brazing process such as Cadweld or equivalent. Special precautions should be taken to minimize corrosion where connections are made of dissimilar metals. Indoor connections can be brazed, silver soldered, or simply bolted together and then tin-lead soldered in the conventional manner. When indoors, don't forget that the steelwork, the ventilation system, and all other metallic objects in the building should also be grounded.
It is mandatory that a good low impedance earth ground be provided for the tower and it is good practice to employ this tower ground for all station ground connections. A system of buried radial conductors, extending outwards from the tower base and from each guy anchor, with their far ends terminated in several ground rods spaced about twice their length apart and driven into the water table, is considered to be a good ground. The steel rebars and J-bolts in footings should also be bonded to this ground system. Be careful of dissimilar metals and don't braze anything to the tower legs! Use stainless steel worm gear style hose clamps to clamp copper strap or copper wires to the tower members. A special conductive grease is available to avoid dissimilar metals corrosion, but frequent inspection is necessary.
Other measures become necessary if the tower footing is located on solid bare rock. These include setting the grounding radials in poured concrete (which has good conductivity), doping with conductivity-enhancing chemical salts such as magnesium sulphate (Epsom salts are supposed to be less environmentally harmful than others), and using special hollow ground rods that are intended to be driven into holes drilled in the rock and which are said to bond chemically to the rock and provide excellent grounding, as long as they are kept filled with water or chemical solution.
The building layout should place the tower, its wiring, transmission line, the AC panels and surge suppressor, and the telephone terminations all near one another so that all ground connections are as short as possible; all indoor equipment should be grounded to the same "technical ground" which we suggest should be the bulkhead plate, which will become a good low impedance ground when connected with several 150mm copper straps to the tower. This single technical ground will provide the basis for lightning protection of all equipment in the building. Both the power company and the telephone company should also use this same technical ground, otherwise a lightning hit to the tower could easily induce damaging transients that ba ck up through the equipment and out the power or phone line to its own ground connections. Surge suppressors for coax lines and other tower circuits can mount (and ground) on the bulkhead plate.
Many installations in large cities make use of existing tall buildings or specifically dedicated structures (such as the CN Tower in Toronto, Ontario, Canada), and grounding for these installations could present a slight challenge.
Most tall structures are provided with wide copper straps running from top to base and grounded at or under the building foundations. The structural steel is also grounded to the same point. The challenge occurs when the structure sustains a lightning hit, because an enormous voltage gradient will be present from top to bottom. Equipment grounding must be done to one point only.
PUB14-01Rev 0 April 10, 2014 2 DTR10SC General Information & Installation
GENERAL INFORMATION AND INSTALLATION
Although most audio and video signals around the transmitter plant are of relatively high levels, it is well to be aware of another planning aspect; this is the possibility of inadvertent creation of one or more "ground loops" of the kind that can induce hum into low level audio circuits.
The most common cause of the hum-inducing kind of "ground loop" is a result of code-approved electrical work in which all wiring is placed inside metallic conduit or raceway, and the conduit is attached to, and in contact with, the grounded structural steelwork of the building.
Here is what can happen: 1. The transmitter cabinets are grounded; 2. The electrical service panels are grounded; 3. The conduit or raceway additionally may be grounded through its fasteners to the structural steel; 4. The service panel is connected by the metallic path through a conduit or raceway to the transmitter cabinet. The result is one or more large area single turn loops that have AC induced in them due to the wiring in the conduit, but which can induce significant hum currents into low level audio wiring.
Suggested treatment for these AC ground loops, is simply to break each metallic loop by using a short length of non-metallic duct on the end of the metallic raceway, or use a short non-metallic section or a non-metallic coupling in the run of conduit. This non-metallic part should be located as near as possible to the cabinet. IMPORTANT:
Non-metallic parts used for electrical work must not be able to burn, nor emit hazardous gases when subjected to flames. You will need to work out the exact ground loop treatment method with your electrical contractor,
and probably with your local electrical inspector as well. This grounding treatment is acceptable to most regulatory authorities in North America and perhaps elsewhere as well,
provided that the equipment in fact is grounded through the copper ground conductors, the bulkhead plate, and solid tower ground. Note that this method does require installation of a separate dedicated grounding wire inside each
conduit for the connection of the isolated ground contact of each receptacle, wherever receptacles are used. It is assumed that isolated ground receptacles are available, usually for use in computer rooms and in hospitals.
It may be necessary that you and your electrical contractor also become technical instructors, in order to reassure your electrical inspector that reduction of ground loops does not in fact contravene the applicable codes. At the very least you will probably need to prove that all your equipment is indeed grounded, despite the non-metallic connection of conduit or raceway.
Other, less severe, ground loops can result from the outer conductors of coax cables being grounded to the chassis of the equipment at both ends of the cable, and of course these components are also grounded through the cabinets in which they mount. The transmission line is grounded at the tower, at the bulkhead, and at the transmitter.
Treatment of coax cable ground loops usually consists of coaxial cable dress in such a manner as to minimize the area presented by the loop. Lowering the line bridge between the building and tower will indeed reduce the loop area presented by the transmission line, but more importantly a lowered line bridge significantly reduces the energy induced on the center conductor due to a direct lightning hit to the tower. 100 to 130cm (3-4 feet) above grade is the suggested maximum bridge height.
PUB14-01Rev 0 April 10, 2014 3 DTR10SC General Information & Installation
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